Lowestoft and Great Yarmouth regional Astronomers based in Lowestoft and Kessingland Astronomy group which is part of Lyra based in Kessingland

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Monday, 3 February 2014

SPA ENB No. 369

The SOCIETY for POPULAR ASTRONOMY

Electronic News Bulletin No. 369 2014 February 2

Here is the latest round-up of news from the Society for Popular Astronomy. The SPA is Britain's liveliest astronomical society, with members all over the world. We accept subscription payments on-line at our secure site and can take credit and debit cards. You can join or renew via a secure server, or just see how much we have to offer by visiting http://www.popastro.com/

WATER DETECTED ON DWARF PLANET CERES NASA

The spacecraft called Dawn, which has spent more than a year orbiting the large asteroid Vesta, is now on its way to Ceres, where it is scheduled to arrive in the spring of 2015. For more than a century, Ceres was known as the largest asteroid in the Solar System, but in 2006 the International Astronomical Union, the governing organization responsible for naming planetary objects, re-classified it as a 'dwarf planet' because of its large size -- it is roughly 950 km in diameter. (But it is still an asteroid, for all that!) When it was discovered in 1801, astronomers thought that it was a planet orbiting between Mars and Jupiter. Later, other cosmic bodies with similar orbits were found, marking the discovery of the Solar System's main belt of asteroids. Scientists think that Ceres contains rock in its interior, with a thick mantle of ice that, if melted, would amount to more fresh water than exists on the Earth. The materials making up Ceres probably date from the first few million years of the Solar System's existence and accumulated before the planets formed.

Scientists using the Herschel infrared space observatory have recently detected water vapour on Ceres. It appears that plumes of water vapour shoot up when portions of its icy surface warm slightly. Until now, ice had been thought to exist on Ceres but had not been detected conclusively. Herschel did not see water vapour every time it looked: although it observed water vapour four different times, on one occasion there was no such signature. Scientists think that, when Ceres is in the part of its orbit that is closest to the Sun, some of its icy surface becomes warm enough to cause water vapour to escape in plumes at a rate of about 6 kilograms per second, while in the colder part of its orbit no water escapes. The strength of the signal also varied over hours, weeks and months, because of the water-vapour plumes rotating in and out of Herschel's view as Ceres spun on its axis. That enabled the scientists to localize the sources of water to two dark spots on the surface of Ceres, previously seen by the Hubble Space Telescope and ground-based telescopes. The dark spots might be more likely to outgas because dark material absorbs heat better than light material. When Dawn arrives, we can hope to learn a lot more.

MILKY WAY MAY HAVE FORMED OUTWARDS FROM THE INSIDE University of Cambridge

Observations of the chemical composition of stars in the Milky Way's disc, particularly, in the study reported here, the fast-produced element magnesium, allow astronomers to estimate how rapidly different parts of the Milky Way were formed. The research suggests that stars in the inner regions of the Galactic disc were the first to form, supporting ideas that our Galaxy grew from the inside out. Using data from the 'Very Large Telescope' in Chile, an international team of astronomers observed stars with a wide range of ages and locations to determine their 'metallicity' -- the amount of chemical elements in a star other than hydrogen and helium, the two dominant elements. Immediately after the Big Bang, the Universe consisted almost entirely of hydrogen and helium, with levels of metallic elements growing over time. Consequently, older stars in general have lower metallicities. The different chemical elements are created at different rates -- some in massive stars which live fast and die young, and others in Sun-like stars with more sedate multi-billion-year lifetimes. Massive stars, which have short lives and die as 'core-collapse supernovae', produce huge amounts of magnesium when they explode. The team has shown that older, 'metal-poor' stars inside the Solar Circle -- the orbit of the Sun around the centre of the Milky Way, which takes roughly 250 million years to complete -- are far more likely to have high levels of magnesium than those outside. The higher levels of the element inside the Solar Circle suggest that that area contained more stars that 'lived fast and died young' in the past. The stars that lie outside the Solar Circle are predominantly younger, both 'metal-rich' and 'metal-poor', and have surprisingly low magnesium levels compared to their general metallicity.

That observation may signify important differences in stellar evolution across the Milky Way's disc, with short star-formation time-scales occurring inside the Solar Circle whereas outside the Sun's orbit star-formation took much longer. That supports certain theoretical models for the formation of disc galaxies, which predict that galactic discs grow from the inside out. The new research also bears on an apparent 'double structure' in the Milky Way's disc -- the so-called 'thin' and 'thick' discs. The thin disc hosts spiral arms, young stars, giant molecular clouds -- all objects which are young, at least in the context of the Galaxy. But astronomers have suspected that there is another disc, which is thicker, shorter and older, and has many old stars that have low metallicity. In the new research, the team found that stars in the young, 'thin' disc aged between 0 and 8 billion years all have a similar degree of metallicity, regardless of age in that range, with many of them considered 'metal-rich'. Then there is a steep decline in metallicity for stars aged over 9 billion years, typical of the 'thick' disc, with no detectable 'metal-rich' stars found at all over that age. But stars of different ages and metallicity can be found in both discs; there is no clear separation between the thin and thick discs. The proportion of stars with different properties is not the same in both discs -- that's why we think that the two discs probably exist -- but they could have very different origins. The study provides evidence that the inner parts of the Milky Way's thick disc formed much more rapidly than did the thin-disc stars, which dominate in our neighbourhood.

Astronomers have discovered a distant quasar illuminating a vast nebula of diffuse gas, revealing for the first time part of the network of filaments thought to connect galaxies in a 'cosmic web'. Using the 10-m Keck I telescope in Hawaii, the researchers detected a gaseous nebula extending about 2 million light-years across intergalactic space. It is an exceptional object, at least twice as large as any nebula detected before, and it extends well beyond the galactic environment of the quasar. The standard cosmological model of structure formation in the Universe would like galaxies to be embedded in a cosmic web of matter, most of which (about 84%) is invisible dark matter. The web appears in the results from computer simulations of the evolution of structure in the Universe, which show the distribution of dark matter on large scales, including the dark-matter haloes in which galaxies form and the cosmic web of filaments that connect them. Gravity causes ordinary matter to follow the distribution of dark matter, so filaments of diffuse, ionized gas are expected to trace a pattern similar to that seen in dark-matter simulations. Until now, however, such filaments have never been seen. Intergalactic gas has been detected by its absorption of light from bright background sources, but those results do not show how the gas is distributed. In this study, the researchers detected the fluorescent glow of hydrogen gas resulting from its illumination by intense radiation from the quasar. The quasar is illuminating diffuse gas on scales beyond any seen before, giving us the first picture of extended gas between galaxies. If the cosmic web is as ubiquitous as some theoreticians would have us believe, however, it seems strange that, with all the interest that there has been in quasars, none of them has ever seemed to have illuminated such material before.

The hydrogen gas illuminated by the quasar emits far-ultraviolet light known as Lyman-alpha radiation. The distance to the quasar is so great (about 10 billion light-years) that the wavelength of the emitted light is red-shifted by the expansion of the Universe into the observable spectrum by the time it reaches here. The researchers imaged the quasar through a filter that passed just the light that had started out at the Lyman-alpha wavelength. The light from the quasar is like a torch beam, and in this case they were lucky that the beam is pointing towards the nebula and making the gas glow. It has been suggested that the nebula may be even bigger than it appears, but we only see the part of the filament that is illuminated by the beamed emission from the quasar.

INVENTOR OF THE POPULAR DOBSONIAN TELESCOPE DIES AT 98 Universe Today

John Dobson, famous as the creator of the simple, low-cost Dobsonian telescope, passed away on 2014 Jan. 15 at the age of 98. Dobson was born in Beijing, but moved with his parents to San Francisco in 1927. After spending 23 years in a monastery, some of which time was spent sneaking out to build telescopes and observe the night sky, he left to co-found the San Francisco Sidewalk Astronomers in 1968, a group dedicated to showing people on the street the wonders of the night sky using what were (for the time) large telescopes.

Dobson's interest in astronomy started in the early 1950s when he built a small telescope from parts obtained from a junk shop. He wanted to see for himself what the Universe looked like. By 1956, he got hold of a 12-inch slab of porthole glass and ground it into a mirror following instructions from Allyn J. Thompson's classic book 'Making Your Own Telescope'. Dobson shook up the amateur telescope- making universe with an innovative design based on simplicity. Most telescopes of his day were small refracting telescopes or small to modest-sized reflectors with metal tubes and heavy equatorial mounts. Neither was exactly user-friendly nor offered much light. John used simple materials like porthole glass, cardboard tubes and wooden altitude-azimuth mounts to build large telescopes that were incredibly easy to use. While such mounts were nothing new, Dobson combined cheap materials, large mirrors and a simpler approach to mountings that made his telescope style unique.

The combination of short days, low Sun, and frequently cloudy weather tested the patience of many of us in November. Despite the difficulties, between us we observed the Sun on all but two days in the month. For those who were blessed with clear skies and steady air there was plenty to see and image in white light and H-alpha.

Rotation Nos. 2143 and 2144: The Mean Daily Frequency remained nearly level, slightly up from 5.10 in October to 5.26. The Relative Sunspot Number also rose slightly from 71.65 in October to 80.47 in November.

WHITE-LIGHT ACTIVITY: At the beginning of November all sunspot activity appeared in a long line along the southern hemisphere of the solar disc. AR 1884 and AR 1885 (a grouping of sunspots that resembled the Southern Cross in the southern night sky) was just past the Central Meridian (CM). AR 1882 and AR 1888 were approaching the west. A fairly large group, AR 1890, appeared over the SE limb on the 3rd. It was not visible to the naked eye at first, but as it crossed the disc it became visible to the protected naked eye on the 8th and 9th. It showed a very complex structure and on the 11th I noticed that the leader spot had several umbrae and a mixture of spots and fragments of penumbrae following the leader.

As AR 1890, which by then was decaying, neared the western limb, the 12th saw some more sunspot activity near the SE limb particularly AR 1895 and 1897, which appeared as a long fragmented grouping of sunspots with many umbrae and numerous pores. AR 1899, a large single spot, appeared foreshortened as it was very close to the E limb. It was preceded by AR 1896, a single spot. AR 1899 was visible to the naked eye from the 15th to the 22nd, probably because it was a single large sunspot. As it neared the W limb sunspot activity declined, leaving AR 1903 at the CM on the 23rd. There were few observations for the last week of November but it seems that sunspot activity was at a low level until the 27th when more sunspots appeared over the E limb.

H-ALPHA ACTIVITY: A tall complex prominence was very clearly seen on the W limb on the 1st, as were a slightly smaller hedgerow near the S limb and some detached cloud-like prominences on the NE limb. Filaments and plages were seen near to the highly active AR 1882, 1884 and 1885 as well as near the SE limb. The 4th was very active with plenty of dark filaments and bright plages all across the disc. There were also some very nice spike prominences along the limb but especially on the east where there was a impressive hedgerow-type prominence. By the 9th and 10th, with AR 1890 near the CM, that region was bright with plage activity. There were several dark filaments elsewhere across the solar disc, and prominences on the S and W limbs and particularly the NE limb where some tall ones were on show.

A Section member reported on the 12th that he had imaged a bright- edged prominence on the E limb associated with AR 1899 that almost resembled a flare. There were also some really nice prominences around the solar limb, particularly one on the SE limb that showed fragmented arches within it, a very active NW limb, and a bright detached one that was clear of the W limb. Filament and plage activity associated with AR 1893, 95, 96 and 99 continued to dominate from the 14th onwards as they crossed the disc. On the 19th an extensive hedgerow prominence was seen on the NW limb, some of it near to sunspot group AR 1893.

MDF (P): 7.84

Go to the Solar Section link on the SPA homepage to see a selection of the many remarkable images and drawings made by the Section membership.

Bulletin compiled by Clive Down

(c) 2014 the Society for Popular Astronomy

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Good Clear Skies--Astrocomet--Colin James Watling

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Various Voluntary work-Litter Picking for Parish Council (Daytime) and also a friend of Kessingland Beach (Watchman) --

--Real Astronomer and head of the Comet section for LYRA (Lowestoft and Great Yarmouth Regional Astronomers) also head of K.A.G (Kessingland Astronomy Group) and Navigator (Astrogator) of the Stars (Fieldwork) --Information

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Astrocomet

I started in Astronomy in 1997 when the Comet Hale Bopp got me interested in Astronomy and Skywatching, since then I have joined Lyra and have vastly improved my knowledge of this very rewarding science.